Hatch said his supporters believe his role as chairman of the powerful Senate Finance Committee is too important to give up. He has up to four more years as chairman.
McMullin told The Salt Lake Tribune he and Hatch had a "friendly discussion about a variety of challenges facing the country."
"He's a nice man and has served our country for decades," McMullin said of Hatch. "I haven't decided if I'll run for Senate or another office in 2018. I'll make that decision based on what is best for the future of Utah and our nation."
McMullin said the meeting was impromptu, while Hatch's office noted the senator had met with McMullin and others after the election in an effort to unite Republicans behind a conservative reform agenda.
"Working together is especially important as Republicans will soon control the House, the Senate and the presidency, and must take advantage of a unique opportunity to make meaningful progress for the American people," Hatch's office said in a statement.
When approached by reporters, Hatch said McMullin is "a very decent guy, as far as I'm concerned. … I think he has a future."
When asked what he thought of McMullin running for his seat, Hatch jokingly said: "That'd be his right, but that'd be a big mistake."
McMullin, who lives in Washington, D.C., was born in Provo, attended Brigham Young University and, like Hatch, is a member of Utah's predominant faith, The Church of Jesus Christ of Latter-day Saints. His independent presidential bid, intended to block GOP nominee Donald Trump from victory, garnered serious support in Utah. He logged 21 percent of the vote, according to the unofficial tally, the highest percentage any third-party candidate this year received in any state. If he were to run, he'd have to relocate to Utah before the 2018 election. If he jumped in, it is not clear if he'd compete as a Republican or as an independent.
Utah Republicans rumored to be considering a run for Hatch's seat include former Gov. Jon Huntsman, Attorney General Sean Reyes and state Sen. Deidre Henderson, R-Spanish Fork.
Alan Crooks, Reyes' campaign manager, said: "You never rule anything out, however he is pleased to serve as attorney general."
Henderson deflected as well, saying: "All of my energy is currently focused on representing my constituents and preparing for the upcoming legislative session."
Huntsman didn't respond to a question of whether he would run himself but heaped praise on Hatch.
"Senator Hatch is beloved in the state, and his decision on seeking an eighth term will no doubt have an impact on how things evolve," Huntsman wrote in an email. "I've long believed in term limits for members of Congress, but Orrin has always worked hard for the people of Utah — and for almost half a century. He's pretty amazing!"
At this stage, no Democrat appears to be seriously considering a run, but Utah Democratic Party Chairman Peter Corroon is keeping an eye on Hatch's decision.
"We appreciate his many years of service, but there comes a time when you have to pass the torch to a new generation," he said, "and the Democratic Party may be part of that effort, if he's unwilling to do so."